Miniature precision bearings for minisystems or microsystems and method for assembling such systems

ABSTRACT

The aim of the invention is to obtain a cost-effective solution for providing a microsystem with bearings, which have sufficiently high precision and long-term stress resistance. The invention proposes a method for manufacturing, adapting or adjusting a bearing portion in a fluidal microcomponent (M) comprising a stator ( 30 ) and a rotor ( 40,2 ). Said rotor is rotatably supported on the at least one bearing portion (L 10 ,L 11 ) relative to said stator. Said rotor ( 40,2 ) is rotatably supported by a sleeve ( 10, 11 ) inserted into said stator ( 30 ), for forming said bearing portion, the at least one sleeve being inserted in said stator as a bearing sleeve and comprising an inner surface and an outer surface ( 10   i,    10   a   ; 11   i,    11   a ). Before being inserted in said stator, said bearing sleeve ( 10, 11 ) is a separate bearing component comprising an inner surface ( 10   i   , 11   i ) as an inner bearing surface, which is mechanically micro-finished before being inserted into said stator ( 30 ). The outer surface ( 10   a   , 11   a ) of said bearing component ( 10, 11 ) is mechanically permanently connected with said stator ( 30 ).

The invention relates to a method for at least one of manufacturing,adapting and adjusting a bearing portion in a mini to microsystem, sucha microsystem being disclosed in WO 97/12147 (Fraunhofer-Gesellschaft)for example as micropump or micromotor for conveying a fluid or forbeing driven by a fluid.

Due to the small nominal sizes for microsystems, in respect to whichreference is made to the scale drawing of FIG. 1, bearings of outerwheels, inner wheels or shafts, which all together are designated as“rotors”, have to meet exacting requirements. Particularly fortransporting (conveying or driving) non-lubricating media, it isnecessary to use very hard and simultaneously corrosion-resistantmaterials, such as ceramic or hard metal. The application of saidmaterials is useful for all tribologically stressed functionalcomponents of a microsystem, to avoid the use of soft or corrosivematerials with a continuous or stronger abrasion. Abrasion in bearingportions, particularly having small and miniature dimensions in amillimeter range (mini to micro system), quickly results in a breakdownof the whole system.

Further, in view of such small nominal sizes, production engineeringfaces difficulties to constantly keep to the required high-precisiondimensions. These dimensional accuracies are in a micrometer range,required accuracy being in the range of 1 to 2 μm. Particularly the useof eccentrically operating microsystems, comprising two rotors meshingwith each other, so-called micropumps having internal teeth according tothe gerotor principle, require a high-precise observation of theeccentricity, said eccentricity being obtained by two eccentricallypositioned bearing portions. In addition to their radial offset, saidbearings have an axial offset, but are located axially closely to eachother. Thus, for principle reasons, the axes are eccentrically offsetrelative to each other. Said eccentricity requires a precision inmicrometer range, said precision being expensive and complex, if notimpossible from the production-engineering point of view, when usingmetal cutting manufacturing methods with a usual housing structure.

It is therefore an object of the invention to propose a cost-effectivesolution for providing a microsystem of the kind illustrated for examplein FIG. 1 with bearings having the required maximum precision and along-term stress resistance, particularly when operated withnon-lubricating fluids.

Said almost impossible object is achieved by a microsystem according toclaim 20 or a manufacturing method, an adapting method, or an adjustingmethod according to one of claims 1, 35 and 27, for manufacturing atleast one bearing portion of said microsystem.

According to the invention, a mechanically precise joint systemcomprising simple, precise bodies (sleeves) and a “not precisely”manufactured housing (stator) is cost-effectively assembled by aconnecting technique (soldering, gluing, friction-setting), particularlyin connection with two axially spaced apart bearings or bearing portionsand in a dimension of the “rotors” to be bearingly supported in adiameter range of below 15 mm, whereby larger embodiments shall not beexcluded, but smaller diameters meet an increased attention.

Within the scope of the specification of the invention, reference ismade to both, a microsystem and a method for manufacturing a bearingportion of said microsystem, said method describing the microsystemnegatively with respect to spaces and bearing portions being provided,into which said microsystem can then be positively inserted. As far asthe microsystem itself is concerned, the finished state is described, inwhich the manufacturing method is only indirectly perceivable, as can beseen from the subsequent specification in support of the claims.

With regard to claims 1, 35 and 27, it is to be first mentioned that theterm of a hard bearing material is compared to that of a “soft” statormaterial. Said terms are to be understood such that said hard bearingmaterial is for example ceramic or hard metal, for ensuring a long-termstress resistance and a long-term precision of said at least one bearingportion. Said softer stator materials, which can be processed moreeasily by cutting and which can be obtained at a lower cost andprocessed more easily from the production-engineering point of view, areunderstood in contrast to said hard materials. The softer statormaterials receive the substantially small bearing components thatprovide the precision and abrasion resistance required for achieving theinventive object (claim 20).

The stator comprises at least one portion made of a material that can beprocessed more easily by metal cutting, said stator receiving at leastone bearing body made of a hard material. In said bearing body,preferably a sleeve, a rotor is bearingly supported either as shaft, oras outer rotor, or as inner rotor.

Between said hard material and said stator material, there is a portionproviding the mechanically permanent connection, which portion can beobtained in three ways. When a portion of the housing material in thebearing portion is displaced by a mechanical friction-setting operation,a direct, mechanically permanent connection is obtained for bearinglysupporting the bearing component such that after insertion, amechanically permanent connection between said bearing component andsaid stator is obtained and that said bearing component is preciselyaligned (claim 2). An alternative variant for obtaining saidmechanically permanent connection is a hardening of a filling materialduring a period of time, said filling material being inserted into agap, which is present between said bearing component and a slightlylarger inner size of the receiving portion of said stator (claim 3).Said gap can be in a range of between 20 μm and 70 μm, particularlybelow 100 μm. After said hardening, a connection of materials isobtained, which is manufactured mechanically permanent, with a long-termstress resistance, and precisely with respect to its position. Further,the realization of said at least one bearing portion thus formed iscost-effective. A third variant is a combination of the twoabove-described methods, when two axially spaced bearings are provided.Then, said friction setting with a mechanical pressing operation with amechanically direct permanent connection for a bearing support of saidfirst bearing component can be combined with a hardening of a fillingmaterial between said second bearing component and said stator.Initially, the first bearing is inserted by friction setting,mechanically displacing said soft material. Subsequently, the secondbearing is put initially loosely into the stator, supported by saidmechanically already permanent bearing, the center of which is axiallyspaced apart. Subsequently, a positioning of said second bearingrelative to said first bearing, and thus an absolute positioning of saidsecond bearing relative to said stator follows, and a hardening fillingmaterial is inserted between said second bearing and said stator, withwhich filling material the hardening and permanently fixing during aperiod of time is realized. An adhesive effect is obtained in a gap,which is left between said second bearing and said stator, as describedabove.

Preferably, the first bearing portion, which is positioned mechanicallyby displacing a surface portion of the stator material, is that of ashaft, the outer diameter of the sleeve, which forms said bearingportion, being smaller than the sleeve, which forms the subsequentlydetermined second bearing portion, which is accurately positioned by thehardening of a filling material (one of claims 5, 31 and 32).

The displacement or the portion filled up with a hardening material isthe portion, which is to be described as “non-fitting portion”, “notproperly dimensioned fit” or “misfit” (compare claim 27). During themanufacturing process, said misfit or not properly dimensioned fitbecomes a fit. The non-fitting portion is obtained either by amechanical displacement of a portion of the stator material (claim 24,26), or said misfit becomes a mechanically permanent connection byproviding a hardening intermediate material, which, as filling materialrealizes said mechanically permanent connection.

During friction setting, said bearing body is guided high-preciselyduring the entire friction setting operation, to obtain an accurateposition in said stator (claim 7). During said mechanical guiding anddisplacement process, at least the surface of the stator portion, whichreceives said bearing component, is modified, particularly more than thesurface or a radial portion is displaced (claim 7, claim 26).

The hardening of a filling material (claim 25, claim 3 and 4) operateswithout displacement, the bearing component being supported accuratelypositioned during hardening, to make said mechanically permanentconnection an accurately positioned precise connection.

Said at least one bearing body, which, before finishing the fabrication,was a bearing body separate from said stator and made from a differentmaterial, is processed by mechanical micro-finishing of the innersurface, for example by grinding, honing or lapping (claim 6), to obtaina suitable bearing support surface for the shaft or the outer rotor.Particularly rotationally symmetrical bearing bodies are suited forgrinding operations, such as centerless grinding, and can bemanufactured comparably inexpensively in the required precision.Additionally, grinding allows processing of hard materials withoutrestriction, the material selection thus not being limited. Afterhigh-precisely manufacturing the bearing support surfaces, themechanical connection with the stator is carried out, the insertion ofthe bearing sleeves and their relative alignment, particularly by gluingor friction setting, being effected with a separate arrangement, saidarrangement defining the position and orientation of said one bearingportion, particularly two eccentric bearing portions (claim 21, 22 and23), and realizing the required tolerances with a comparably low effortor cost.

Prior to a hardening of the solder or the adhesive substance, thesleeves can be adjusted relative to each other, so that said sleevesinitially float and are aligned in said gap filled with adhesive.

A supporting arrangement serves for stabilizing the position and forsecuring it during the proceeding hardening of said solder or adhesive.

The manufacturing method advantageously limits the variety of parts of amodular system of parts comprising different rotor sizes of the toothring pump, since identical bearing bodies can be used for differenttooth systems—defined by the eccentricity and the tooth parameters.

Friction setting is done with a slight press fit, the manufacturingtolerance of a “not sufficiently precise” stator, e.g. a statormanufactured by cutting (by a metal cutting method) defining theoversize of the fit. As the tolerance of the position of the negativemold in the housing does usually not correspond to the position of thecorresponding bearing bodies, the material is displaced during thefriction setting operation. In most cases, said operation occursasymmetrically and is enabled by the roughness and by a defined smallsupporting portion on the surface of the negative mold. The roughness ofthe surface to be produced is adjusted such that tips of the surface,which carry the bearing body to be pressed in, can be displacedrelatively easily. Alternatively, the surface results from a definedaxial or radial structure (comparable to a peg). The radial offset to becompensated between the bearing body and the portion of the statorreceiving said bearing body can be around 10 μm to 20 μm.

The principle of said bearing support can also be transferred to othermechanical systems with defined bearings, such as pumps having externalteeth, etc., so that the invention does not imperatively relate to axeswith two bearing portions only.

A rough determination of the position of the bearing bodies isinexpensively predetermined by metal cutting methods (lathing, millingor the like) or basic (original) shaping (e.g. by injection molding),reshaping or other manufacturing methods. The recesses (negative molds)have dimensions of a limited precision, thus possibly having largertolerances than directly provided bearing portions. This already reducesthe manufacturing cost, to subsequently obtain the precise and accurateposition of the bearing bodies relative to each other by using theassembly arrangement, which high-precisely positions the hard bearingbodies in the comparably soft stator and determines their relativeposition and alignment with a micrometer accuracy.

A separate substantial assembly arrangement, which is describedhereinafter, is of decisive influence for all assembly operations. Dueto its geometry, which is of micrometer accuracy, said assemblyarrangement defines the eccentric position of the sleeve axes relativeto each other and stabilizes said position during the assemblyoperation, either during friction setting or during the supporting time,during which the adhesive material hardens.

The bearing support is designed to correspond to a so-called flying(unilateral) bearing support (claim 9). Said unilateral bearing portionis closer to the drive means than the backside of the bearing support,which is occupied by the microsystem. Said unilateral bearing supportallows reducing the number of bearing portions requiring precision.Therefore, by using a bearing sleeve receiving a rotor (outer rotor,inner rotor or shaft), a radial bearing support of the rotatingfunctional element can be ensured. When two bearing supports that arearranged eccentrically relative to each other are provided, the bearingbody serves as an axial support for the outer rotor of the microsystemfor forming the shaft bearing (claim 15 to 18). With respect thereto,the inner diameter of the bearing body for the shaft is smaller than theinner diameter of the bearing body for the outer rotor of themicrosystem. As also the outer diameter of the bearing body for theshaft is larger than the inner diameter of the bearing body for theouter rotor, an axial bearing surface is obtained. Thus, the outer rotor(and the inner rotor) is in surface contact With the axial face endsurface of the bearing component having the smallest inner diameter. Astrip is formed between said two bearing components (claim 17), saidstrip not having a constant width in a circumferential direction due tothe eccentricity (claim 18).

The eccentric sleeves are in surface contact with each other along theircomplete circumference (on at least one inner surface) (claim 16) andare particularly mounted on an axial end portion, i.e. on a face endsurface of the stator. On the other end of the stator, a couplingarrangement is provided, said coupling arrangement establishing aconnection with a motor arrangement in the sense of a drive means.

When speaking of a radially offset bearing support and of an axiallyoffset bearing support, reference can be made to the respective centers.As far as said radial offset is concerned, the axes are offset relativeto each other, said offset being represented by the parameter dr. Anaxial offset corresponds to a distance of the centers of the bearingportions, said distance being designated dL. Said two bearing portionsthemselves, however, have a final axial length and are closelyneighboring each other, particularly are directly adjacent to each other(claim 15).

The only spatially limited dimension of the bearing portions also allowsthe use of highly special and expensive materials for said bearingportions, without insubordinately increasing the cost of the entiresystem.

In a mechanical micro-finishing operation relating to the separatebearing component, which prior to inserting comprises a surface suitableas an inner bearing surface, a rectangularity of said inner bearingsurface relative to a face end of said bearing component can beobserved. Rectangularity is advantageous for an additional auxiliarysupport in the sense of a mechanical support portion during the assemblyof the bearing portions (claim 14, 17 and 34).

Another adjusting possibility is given in an axial direction, when afirst supporting portion as a first bearing portion is already finished(claim 31 to 33, claim 5). The height (measured in an axial direction)of the bearing portion for receiving said rotor, i.e. the second bearingportion, can be adjusted by manufacturing engineering relative to thestator to obtain a defined face end clearance. Said face end clearancerefers to the rotor inserted later, which is rotatably supported in saidsecond bearing portion. With said face end clearance, the friction andthe fluidal bearing can be predetermined. The inner opening of thestator, into which said at least one bearing portion, preferably twoaxially spaced apart bearing portions are inserted, comprises twoportions (claim 12), each forming an inward directing surface. Saidsurfaces are the surface portions not yet suited for a bearing support,onto which the bearing portions are mounted by said bearing sleeves,which from a production-engineering point of view are more precise,namely by a gluing or pressing method or by a combination of saidconnecting techniques. Said two surface portions of the raw bearing arealready eccentrically aligned relative to each other to form arespective axis each, said axes having an axial distance “dr” in aradial direction.

The inner receiving portion therefore has two functional portions forreceiving two functionally different bearing portions, each comprising arespective bearing body. A compensating function by friction setting orgluing has an effect only in a very small dimensional range, aneccentricity being dependent on the toothing, for example 180 μm, inwhich example a gluing gap is in a range of 70 μm at maximum and apressing oversize is around 10 μm.

The claimed invention is described in detail and supplemented byembodiments.

FIG. 1 is a full scale illustration (1:1) of the complete microsystem 1,said micro system comprising a fluid connection F, the proper fluidtransporting micro component M, e.g. as pump having a motor drive A, oras fluidal motor M having a drive means A.

FIG. 1 a is an exploded and considerably enlarged view of FIG. 1,illustrating all components, which are to be described in more detail inthe following, said micro component M comprising an inner rotor 3 and anouter rotor 2, said inner rotor being mounted on a shaft 40. Said microcomponent is described in more detail in the above-mentioned WO-documentand is therefore designated as gerotor system or as tooth ring systemhaving internal teeth, said teeth being in a meshing engagement duringrotation.

FIG. 2 is a sectional view along a main axis of FIG. 1 a and illustratesan assembly of a tooth ring system with all components.

FIG. 3 illustrates a section along a center axis of the system accordingto the above figures, only a stator 30 being schematically displayed asa housing, for illustrating sleeves 10,11 mounted therein as bearingportions.

FIG. 3 a illustrates surfaces 30 i and 10 a of a bearing sleeve 10 and astator 30 before and after inserting said sleeve.

FIG. 4 shows a supporting and positioning system 50 for inserting saidsleeves 10,11 according to FIG. 3.

FIG. 5 is a perspective view of FIG. 3, showing said stator and, stillspaced apart, i.e. before being mounted, a first sleeve part 10 and asecond sleeve part 11 for receiving said shaft 40 in a shaft space W andan outer rotor of said micro system in a rotor space R. Said two partsare inserted into a provided inner space 31 of said stator in adirection s.

FIG. 6 illustrates an alternative adjustment and permanent fixing ofsaid sleeves 10,11 of FIG. 5, compared to FIG. 3 a.

FIG. 7 is a top plan view of FIG. 3 in an axial direction, still withoutan inserted rotor and without an inserted shaft 40, for illustrating anaxial bearing and supporting surface 10 b.

The full-scale illustration of the microsystem according to FIG. 1 showsthe requirements with regard to a miniaturization and the necessity ofmanufacturing bearings provided in said system with an extremely highprecision and of ensuring their stress resistance and abrasionresistance.

FIGS. 1 a and 2 shall be described together for providing an insightinto the microsystem illustrated in FIG. 1.

The largest portion is occupied by a drive system A, which is connectedwith a micro component over a flange portion. A shaft of a motor isconnected with a shaft 40 of said micro component over a coupling means23, said connection being non-rotating. An inner space 32, provided forthis purpose, is limited by a sleeve 21, said sleeve having a longeraxial extension than a length of said coupling means 23. At said shaft40, a first hat-shaped gasket 24 is provided, said gasket having acollar-shaped protruding thin flange portion and an opening for apassage of said shaft 40. Said gasket is positioned in an axial innerspace 31, in which also a first bearing sleeve 10 is located, saidbearing sleeve also having an inner opening, in which said shaft 40 issuitably supported for rotation.

Above said first sleeve 10, a second sleeve 11 is provided, said secondsleeve having a larger outer diameter and a lager inner opening, forreceiving a rotor or rotors 2,3 of said microsystem M, one of whichrotors being non-rotatably positioned over a pin 40 a on said shaft 40.

When rotating said shaft, both internally toothed rotors rotate withsaid shaft, for which rotation an outer bearing support of the outertoothed ring at said second sleeve 11 is provided.

Said second sleeve 11 has a considerably shorter axial extension, but alarger radial inner opening, whereas said first sleeve 10 comprises asmall opening suitable for said shaft, but extending over a larger axiallength.

The described micro component is generally marked with M, but itcomprises said two internally toothed rotors 2 and 3, as illustrated inFIG. 1 a.

Said sleeves 10,11, said gasket 24, and said shaft 40 are received in astator 30, which can be regarded as a portion of the housing. Saidstator comprises a longitudinally extending flange portion 30 b,extending outside over a distance sleeve 21 and engaging at an edge ofsaid drive A for fixation, and a further above located portion 30 a inwhich said micro system M and said shaft 40 are supported. The stator 30is directly screwed up with the motor. For this purpose, small sizeelectric motors comprise standard threads or connection holes, overwhich motor drives are usually fastened.

The inner opening of said second sleeve 11 for receiving said microsystem M is disposed in said stator at a face end thereof. Said sleevecan be mounted flush with respect to the face end of said stator 30.Preferably, however, a slight projection can be provided to obtain abetter sealing effect at the rotors, when a portion 29,29′, locatedabove said rotors and comprising a fluid guiding means towards theconnections F, is pressed with a higher pressure over a screwed flange28 against said stator 30 with an intermediate sealing ring 25 and akidney plate 25 a. Between said screwed flange 28 and said stator 30,preferably a left-hand thread is provided, which is disposed outside. Aspecial claw tool is used for screwing, said claw tool engaging in alateral bore. Thus, an unauthorized opening is avoided. Said portion29,29′ comprises fluidal control contours (inlet opening and outletopening) and is aligned exactly (radially and circumferentially) withits lower portion 29′ over a cylindrical pin 22 for engaging in a fitopening 22 a in said stator 30, and, if required, in a collar at saidstator 30.

The described flush contact of the lower portion 29′ of the fluidtransporting portion 29,29′ with its surface extending towards saiddrive with said rotors of the fluidal system M is improved by providinga compensating ring 27 between the clamping arrangement 28 and saidfluid transporting portion 29. Said compensating ring 27 is made of asoft material, for example aluminum, copper or plastic, and provides aplane-parallel and flush contact of said portion 29′ with said stator,which is also provided with an O-shaped gasket 25 or an additional diskor plate 25 a with fluid transporting kidneys, particularly alsocontacting the outward-directing face end surfaces of said rotors, forobtaining a better sealing effect. Said better sealing effect isachieved by a higher surface pressure (a more solid seat/contact) ofsaid fluid transporting portion 29′ against said second sleeve 11, saidbetter sealing effect being favored by said soft compensating ring 27.

From the above description, three constructive portions can be taken. Afluid transporting portion F comprising the components 28,29,29′, whichcan also be regarded as stator. The proper stator 30 at a portion 30 a,for receiving a microsystem, said stator comprising an adjacent couplingportion 23 of a shaft 40 at a portion 30 b. Said portion is attached toa drive portion A.

It is emphasized that in said stator, a separation of the fluidtransporting portion 28,29,29′, F from said microsystem takes place,said separation being provided by the assembly and positioned at a faceend of the rotors of the microsystem, said face end directing away fromthe bearing side. In other words, the stator 30 is structured such thatthe bearing support is positioned flush at a face end directing awayfrom said drive A, so that a mounting of said fluid transporting portion29,29′ is directly adjacent to the fluidal micro component and ensures afluid transport and functional operation of said micro component M by aprovided fluid conveying structure comprising kidneys and bores.

The above general view is intended to increase the understanding of theconstructive design and structure of a microsystem according to FIG. 1.In the following, details are explained, which particularly describe themounting and assembly of the first and second sleeve 10,11 according toFIG. 2, reference insofar being made to FIG. 3.

FIG. 3 is a section through an axis of the system according to FIG. 2,two axes 100 and 101 being shown, said axes being offset relative toeach other. Said offset of axes is marked with dr. Said axis 100 is theaxis of the first sleeve 10, said sleeve having a length L10. Saidsleeve is made of a hard material, e.g. hard metal or ceramic.Initially, it is not inserted in the stator 30, said stator having anelongated opening 31 for receiving said sleeve, a lower portion of saidopening having an inner surface 30 i. Said inner surface isschematically illustrated in FIG. 3 a (in the lower part of theillustration). Said surface is of considerable roughness, which can beobtained by a metal cutting method. Said surface does not have to beparticularly precise and can be embodied even larger than illustrated inFIG. 6.

Likewise, a further receiving portion is provided, said receivingportion being disposed axially above in said stator 30 as part of saidopening 31, for receiving said second sleeve 11, which can also be madeof a hard material, such as ceramic or hard metal. Said sleeve, too, isinitially not inserted.

The use of hard materials in contrast to “soft” materials of said stator30 protects the bearing sleeves against abrasion. Said bearing sleevesare of small spatial extension, so that also expensive materials can beused. Said bearing sleeves are preferably designed as hollow cylindersand comprise an inner space each, for receiving the respective “rotor”.

Said first sleeve 10 has an inner space with an inner surface 10 i forreceiving a shaft 40. Said inner space is marked with W and has alongitudinal extension corresponding to said sleeve length L10.

The axially adjacent second sleeve 11 is provided for receiving andsupporting the outer rotor 2. In respect thereto, said sleeve has arotor-receiving portion R, a diameter d11 i of said rotor-receivingportion being larger than a diameter d10 i of said shaft space W. Aninner surface 11 i is designed to allow a bearing support of said rotor.The inner surface 10 i of the first sleeve 10 is also designed to allowa bearing support of said shaft 40.

Both surfaces have a high precision and are designed for theirrespective bearing support function by grinding, eroding, honing, orlapping.

An inserting arrangement according to FIG. 4 is provided for insertingsaid two bearing sleeves into the respective axial portion of theopening 31 of said stator 30 with said inner surface 30 i and said innerradially larger surface 30 i′.

The two sleeves 10,11 are spatially geometrically aligned relative toeach other by place holders 53,52, thus ensuring a high precision. Saidtwo place holders 52,53 are spatially fixed relative to a support plate51. The placeholder 52 for the outer rotor receives said second sleeve11, said placeholder filling up the rotor geometry of the rotor space R.The second placeholder 53 for the shaft 40 is axially longer. Saidsecond placeholder fills up the shaft space W and locates the firstsleeve 10 spatially geometrically, to obtain the two spaced apart axes100,101 for an eccentric bearing support of said microsystem Mcomprising two rotors. A not illustrated pin at said support plate 51provides an absolute determination of the position of said support platein relation to said stator 30, for engaging in an opening 22 a.

After mounting said sleeves 10,11 on said inserting arrangement 50 andsaid two placeholders 52,53 which are radially offset by “dr”, amechanical arrangement (not illustrated) is used for axially moving saidinserting arrangement into said opening 31 of said stator 30, saidmovement being geometrical and precise, even high precise with regard tothe masses. The movement path s or the movement direction s, is shown inFIGS. 5 and 3 a. Due to the dimensioning and the surface structure ofthe two sleeves 10,11 and of the inner surfaces 30 i′ and 30 i of thestator, a modification of at least the inner surfaces of the stator 30occurs, said modification being visible in FIG. 3 a prior to and afterinserting said sleeve part 10. The rough surface of the nothigh-precisely manufactured inner surfaces is leveled or even removed ordisplaced, the soft material being modified on the surface, butsimultaneously applying mechanical forces for spatially geometricallyfixing said pressed-in sleeves 10,11, which serve as bearing supportpieces.

The inner surfaces 11 i,10 i of said two sleeves are high precise, andafter inserting, geometrically precisely fixed to achieve their bearingfunction.

The outer surfaces 10 a and 11 a of the two sleeves enter into amechanical connection with the inner surfaces 30 i′ and 30 i of thestator, when the inserting arrangement 50 is axially introduced underpressure.

An alternative fixation can be provided by a hardening substance 12,when the inner surfaces 30 i′ and/or 30 i are designed to have aslightly larger spatial geometry than the outer surfaces 11 a and/or 10a of said sleeves 10 and/or 11, as illustrated in FIG. 6. In this case,said inserting arrangement cares for an attribution of the eccentricallyoffset axes 100,101 of said two sleeves, and positions them in the innerspace 31 with the two eccentric portions 30 i,30 i′ of the stator 30until an introduced hardening substance 12 fills up a gap 13 for fixingit, and mechanically fixes said sleeves.

A solder or a bonding agent can be used as hardening substance; saidfirst material hardens by a decreasing temperature, said second materialby a chemical reaction.

One function of said inserting arrangement is to take over themechanical attribution during the axial friction setting. Regarding thevariant of fixation with a hardening substance in a gap 13 (also as anirregular interspace), said gap having a size of between 20 μm and 70μm, said inserting arrangement takes over the geometrical fixation ofthe sleeves during hardening, therefore, during insertion, saidinserting arrangement does not have to apply an additional mechanicalforce in a direction s.

The second sleeve 11 is axially shorter and has an axial length L11. Thetotal stator length is L. Said stator 30 having an axial length L, thetotal of said two sleeve lengths L11 and L10 is still shorter than saidstator length. The distance of the centers of said two sleeves is dL,which represents an axial offset, the face end surfaces of said twosleeves 10,11, however, contacting each other. Said contact of the twoface end surfaces is described with reference to FIG. 7.

FIG. 7 illustrates a top plan view in an axial direction 100,101 fromabove (regarded from FIG. 3 or FIG. 6), the inner spaces R and W for theouter rotor and the shaft still being open, thus no shaft 40 and norotor 2 or 3 of a microsystem M being inserted yet. A face-end bearingsurface 10 b is visible, which is also marked in FIG. 3 and in FIG. 6.Said bearing surface has a width b, said width not being constant in acircumferential direction, which results from the offset dr or Δr ofsaid two axes 100,101, and from the two selected diameters of thesleeves, here the outer diameter d10 a of the longer sleeve 10 and theinner diameter d11 i of the shorter sleeve 11. Said diameters and thecorresponding radii as respective half diameters, as well as the radialoffset (eccentricity) are selected such that one of the hard bearingcomponents 10,11 forms an annular axial support surface 10 c, which isoutside of a surface 10 b and completely continuous also in acircumferential direction, and on which the other hard bearing component11 is supported to have surface contact.

When observing said radial offset dr, the outer diameter d10 a of saidsleeve 10 is as much larger as the inner diameter d11 i of said sleeve11 that at no circumferential position, the soft material of said stator30 as a portion of said support surface 10 b for said rotor 2 accordingto FIG. 1 a and possibly also for said inner rotor 3 according to FIG. 1a—regarded in an axial direction—appears or is of importance. The rotoror the rotors are—inserted in said rotor space R—then axially safelysupported, geometrically precisely fixed, and a good sealing is obtainedat the surface 10 b, whereas the annular portion 10 c, which supportssaid sleeves 10 and 11 relative to each other and aligns themorthogonally, is no longer visible from outside.

Inner surfaces 11 i and 10 i form bearing surfaces for the shaft 40 andthe outer rotor of the fluidal microcomponent M, for serving as a slidebearing. Said annular surfaces 10 c and 10 b together form the axiallydirecting face end surface of the complete bearing component 10 providedfor said shaft. Said inner portion 10 b serves for supporting andaligning the microsystem, and the surrounding outer portion 10 c, whichis located on the same level, serves for aligning and supporting saidsecond bearing component 11.

The top plan view according to FIG. 7 also illustrates the gap 13according to FIG. 6, said gap already being filled up with an adhesiveor a solder 12, for fixing the inserted sleeve 11 relative to the softermaterial of said stator 30. Before said solder or adhesive hardens, saidsleeve 11 was aligned by contacting at said outer annular surface 10 cof said lower sleeve 10, so that the axis 101 of said sleeve is alsoaligned precisely in parallel to the axis 100. Said precise alignmentresults from a high-precise manufacturing of the face end surfaces,which extend exactly perpendicularly to said axes and are thus adaptedto have a direct effect on the positioning and exact position. In anembodiment of specific dimensions, which, however, are not to beunderstood as restricting, a sleeve 10 was manufactured having an outerdiameter of 5 mm and an inner diameter of 1.2 mm. An outer rotor 2 hasan outer dimension of 3.8 mm, and is therefore—also when the selectedeccentricity of the two axes 100,101 is considered—within the outerdimension of 5.0 mm of said sleeve 10, axially supporting said rotor forproviding a rotatable bearing support. From said dimension, also theinner size d11 i of said second sleeve 11 is visible, corresponding tothe outer size of said rotor, for radially supporting said rotor with anannular bearing. Both bearing supports, which are perpendicular relativeto each other, the inner wall surface 11 i and the axially directingsupport surface of the sleeve 10 provide a precise alignment and precisebearing support of the rotor component 2.

A gap 13, which for explanatory purposes is illustrated in an oversizein FIG. 7, results from the difference between the radius of the innersurface 30 i′ of the stator 30, compare FIG. 3, and the outer dimensionof the outer surface 11 a of the hard bearing sleeve 11. For a bonding,the size of said gap is preferably between 50 μm and 70 μm, which, whenillustrated to scale, would not be visible in the illustration accordingto FIG. 7, if it had not been represented at a substantially enlargedscale.

FIG. 5 is a perspective view showing the insertion of the two bearingsleeves 10,11, used for an assembly and adjustment of the sleeves withan adhesive substance. An adhesive substance 12 is introduced into a gap13 having a size of between 20 μm and 70 μm with reference to arespective inner diameter of said stator 30 at the surfaces 30 i and 30i′. The inner space 31 for receiving said first sleeve 10 is longer thansaid bearing sleeve 10. The corresponding difference—as illustrated inFIG. 2—is occupied by a radial shaft sealing 24, which is fixed againstsaid motor A by a distance sleeve 21. An inserting path s of the twobearing sleeves 10,11, supported by an inserting arrangement 50according to FIG. 4, provides a precise positioning. After filling in anadhesive substance 12, which can also be present at said inner surfacesaccording to FIG. 5 already prior to said insertion, a spatialgeometrical attribution and an absolute positioning of said sleeves10,11 is maintained for at least the hardening time of said adhesivesubstance or solder, until a mechanical hardening occurs.

Also visible from FIG. 5 is a receiving portion 22 a, in which apositioning pin 22 according to FIG. 2 engages, when mounting a fluidtransporting portion 28,29,29′. A radially offset stepped bore 22 at theinner side of the surfaces 30 i′ and 30 i, respectively, of said stator30 is provided. Circumferentially spaced apart from said receivingportion 22 a, said bore offers a possibility of using a fluid in a smallquantity as slide bearing lubrication or in an annular flow afterinserting and mounting said bearing sleeves 10,11, when operating saidsystem M. Said bore 22 b has a minimum depth of L10+L11. Said steppedbore 22 b, which is also illustrated in FIG. 1 a, is located with aportion of its bore depth in the surface portion 30 i′ (compare FIG. 3)and with a further portion in a surface portion 30 i. By said bore, theannular flow of the fluid, which flows through the shaft bearing, isobtained. By said stepped bore, a discharge of the fluid present betweenthe sealing and the shaft bearing in a direction towards the suctionside of the microsystem is obtained, said microsystem in the presentembodiment being provided as a pump. The fluid from said stepped bore 22b, insofar operating as a channel for said fluid, is again taken up inthe fluid conducting portion 28,29,29′, here in a portion 29′ directingtowards said microsystem by covering said channel, and is returned intosaid microsystem 2,3.

It is to be mentioned, that the spatial-geometrical high-precise bearingsupport is only provided unilaterally with respect to the shaft W, butthat also a second bearing support can be provided in said fluidconveying portion 29, said second bearing support, however, not havingto be as precise as said first bearing support in said sleeve 10, whichis additionally effective on an axially larger length L10.

The bearing portions can be manufactured as sleeves in a rotationallysymmetrical simple manner. They can also have a different geometry withregard to their outer diameter, only their inner diameter and theirinner surface have to be aligned such that the rotors 40,2 (shafts andouter rotor of the microsystem) can be bearing-supported geometricallyprecisely and resistant to abrasion.

The described methods of inserting and positioning can also be combined.

A less solid mechanical connection can be provided for an insertion bypressing in or friction setting the sleeves 10,11, determined by acorresponding adaptation of the diameter geometries of inner space andouter surface of the sleeves. After said friction setting operation, analignment and subsequently a bonding can be effected by an additionalarrangement, so that the two methods can also be used in combination.

The combined inserting method can also be effected temporallysuccessively. The first receiving portion with the inner surface 30 i inthe first portion of the opening 31 of the stator can be connected by amechanical friction setting operation, in which the sleeve is preciselypositioned, as shown in FIG. 3 a. Relative to said first sleeve fixed bysaid method, which sleeve can then serve as an auxiliary bearing or anauxiliary arrangement, the second bearing portion (here with the sleeve11) can be positioned in the portion L11 with the arrangement accordingto FIG. 4, a gap 13, illustrated in FIG. 6 being filled with an adhesivesubstance 12 at a circumference between the outer surface 11 a and theinner surface 30 i′. When said first sleeve 10 fits solidly, said secondsleeve can be positioned and bonded relative to said first sleeve andconsequently relative to said stator. As an alternative to said bondingoperation, a pressing operation can also be used for said secondoperation, which corresponds to the variant described before, onlytemporally successively. The arrangement according is to FIG. 4 can beused for all these variants.

A combination of pressing (friction setting) and gluing (bonding) turnedout to be particularly precise. Initially, the first sleeve 10 ispressed into the stator 30, the two opening portions 30 i,30 i′ beingprovided as two portions of the complete opening 31, said portions beingpositioned eccentrically with respect to each other. After pressing in,the second support portion 11 is formed by inserting a high-preciselymanufactured bearing sleeve into the housing, said bearing sleeve beingin a flush surface contact with said first sleeve, at a face end surfaceportion 10 c thereof. Subsequently, the position of the second sleeverelative to said first sleeve is defined by using the arrangementaccording to FIG. 4. Subsequently, an adhesive substance 12 isintroduced into the gap 13 at the outer surface 11 a of said secondsleeve and hardened, to fix said bearing portion, i.e. to permanentlyconnect it with said stator 30.

The rectangularity of the preceding mechanical micro-finishing of saidsleeve 11 and of said sleeve 10 can provide two auxiliary bearingportions for positioning and fixing. An axial support surface 10 c and acircumferential inner surface 10 i which, over the arrangement accordingto FIG. 4, can directly influence the precise positioning of said secondinserted sleeve.

The mounting order of the two sleeves 10 and 11 can also be exchanged.Firstly, said sleeve 11, which is larger in diameter,subsequently—axially supported over the support surface portion 10 c—thelonger sleeve 10 for the shaft 40. In this case, said second sleeve 10is inserted into the lower receiving portion of the opening 31 from acoupling space 32.

It is mentioned that said mechanically precise positioning in the senseof a spatial-geometrical fixing concerns two substantial dimensions. Onthe one hand, the amount of the eccentricity vector “dr” as radialoffset. On the other hand, the correct absolute positioning of the twobearing sleeves 10,11 in the stator 30, thus their position/alignmentrelative to the housing. Said position is obtained over a pin, which ismounted in the plate 51 of the arrangement 50 according to FIG. 4 andengages in said housing instead of a pin 22 a, when mounting saidbearing sleeves 10,11. Said pin is not illustrated in FIG. 4, but it isevident from the context and from the spatial/geometrical positioning ofthe receiving means 22 a of FIG. 2, in which the pin 22, providing thefinished assembly is marked. Said pin takes over the circumferentialfixing of the fluid conveying portion 28,29,29′ relative to the housing30, which is designated as stator.

1. Method for at least one of manufacturing, adapting and adjusting atleast one bearing portion in a fluidal mini to micro component (M), saidcomponent comprising a stator (30) and at least one rotor (40,2), saidrotor being supported at said at least one bearing portion (L10,L11)relative to said stator to be rotatable and rotatably supported;characterized in that (a) said rotor (40,2) is rotatably supported by asleeve (10,11) inserted in said stator (30), for forming said bearingportion, said at least one sleeve is inserted in said stator as abearing sleeve and comprises an inner surface and an outer surface (10i,10 a; 11 i,11 a); (b) said bearing sleeve (10,11), prior to insertingin said stator, is a separate bearing component, comprising an innerbearing surface as said inner surface (10 i,11 i), and said bearingsleeve is mechanically micro-finished on at least said surface prior toinserting in said stator (30); (c) said outer surface (10 a,11 a) ofsaid bearing component (10,11) is brought into a mechanically permanentconnection with said stator (30).
 2. The method of claim 1, wherein saidouter surface (10 a,11 a) of said bearing component (10,11) is insertedby friction setting into a receiving portion (30 i,30 i′) of saidstator, said receiving portion having a smaller inner dimension, wherebya particularly radial displacement of a surface portion of a softermaterial of said stator is effected by said bearing sleeve (10,11), forproviding a mechanically permanent connection with said stator (30). 3.The method of claim 1, wherein said outer surface (10 a,11 a) of saidbearing component (11,10) is inserted into a receiving portion of saidstator (30), said receiving portion having a larger inner dimension, anda gap (13) or an irregular interspace between said bearing component andsaid receiving portion is provided with a hardenable filling material(12), said filling material hardening after being filled in, for amechanically permanent connection of said bearing component (10,11) withsaid stator (30).
 4. The method of claim 3, wherein said hardening isobtained by one of cooling down, particularly when a solder is used asfilling material, and a chemical reaction, particularly when an adhesivesubstance is used as filling material (12).
 5. The method of claim 1,wherein at least two axially spaced bearing portions (L10,L11; 10,11)are provided in said stator (30), one of said bearing portions beingformed by a first sleeve (10) and the other of said bearing portionsbeing formed by a further sleeve (11), said first sleeve being fixed andsaid second sleeve being fixed to said stator (30) and relative to eachother.
 6. The method of claim 1, wherein said mechanical micro-finishingof said inner surface (10 i,11 i) of said bearing component is one ofgrinding, honing, and lapping.
 7. The method of claim 2, wherein duringthe entire inserting operation, said bearing component is guided andsupported (50) by a mechanical contact, to result in an accuratelypositioned bearing component in said stator (30) during said frictionsetting.
 8. The method of claim 3, wherein said bearing component(10,11) is supported in an accurate position during hardening, forobtaining an accurately positioned alignment of said supported bearingcomponent in said stator (30) after said hardening.
 9. The method ofclaim 1, wherein said bearing portion is a unilateral bearing,particularly being positioned in said stator (30) as housing, such thatsaid bearing portion is closer to a drive than said microsystem (M). 10.The method of claim 1, wherein said at least one bearing component(10,11) has a cylindrical shape, particularly also an outer cylindricalshape.
 11. The method of claim 1, wherein a first and a second bearingbody (10,11) each being shaped as a sleeve, and each defining an axis(100,101), said two sleeves being mounted in a housing (30,31) asstator, to have eccentric or radially offset (dr) axes relative to eachother, and to be axially offset, for obtaining a bearing support at anaxial distance (dL) or non-identical axial positions (L11,L10) for ashaft (40) and a bearing support for an outer rotor (2) as two rotors.12. The method of claim 1, wherein two bearing components are insertedinto said stator, into two axially spaced portions (30 i,30 i′) of aninner opening (31) of said stator (30), and wherein said two portions ofsaid opening (31) are designed eccentrically with respect to each other,for attributing each of two rotors to one of said two bearing componentsfor being rotatably supported.
 13. The method of claim 1, wherein atleast two axially spaced bearing portions (L10,L11; 10,11) are providedin said stator (30), one of said bearing portions being formed by afirst sleeve (10) and the other of said bearing portions being formed bya further sleeve (11), said first sleeve being fixed and said secondsleeve being fixed relative to said stator (30) and relative to eachother; and wherein two bearing components are inserted into said stator,into two axially spaced portions (30 i,30 i′) of an inner opening (31)of said stator (30), and wherein said two portions of said opening (31)are designed eccentrically with respect to each other, for attributingeach of two rotors to one of said two bearing components for beingrotatably supported; and wherein said first bearing component (10) isprovided for supporting said shaft (40), and said second bearingcomponent (11) is provided for supporting said rotor (2).
 14. The methodof claim 12, wherein said first bearing component (10) has an outerdiameter of an outer surface (10 a) with a first diameter (d10 a), andsaid second bearing component has an inner diameter of an inner bearingsurface (11 i) with an inner diameter (d11 i), said inner diameter beingsmaller than said outer diameter, for an axial supporting surface (10 c)between said bearing bodies (10,11) in a difference portion; for anaxial bearing surface (b,10 b) within said inner diameter.
 15. Themethod of claim 1, wherein said at least one bearing component is afreely shaped bearing body, having an inner surface (11 i,10 i) suitablefor a bearing support.
 16. The method of claim 11, wherein said radialoffset (dr) and said inner diameter and said outer diameter (d10 a,d11i) are coordinated such that said two bearing bodies contact each othercircumferentially continuously at a face end, at a support surface ring(10 c).
 17. The method of claim 1, wherein a first and a second bearingbody (10,11) each being shaped as a sleeve, and each defining an axis(100,101), said two sleeves being mounted in a housing (30,31) asstator, to have eccentric or radially offset (dr) axes relative to eachother, and to be axially offset, for obtaining a bearing support at anaxial distance (dL) or non-identical axial positions (L11,L10) for ashaft (40) and a bearing support for an outer rotor (2) as two rotors;and wherein two bearing components are inserted into said stator, intotwo axially spaced portions (30 i,30 i′) of an inner opening (31) ofsaid stator (30), and wherein said two portions of said opening (31) aredesigned eccentrically with respect to each other, for attributing eachof two rotors to one of said two bearing components for being rotatablesupported; and wherein said first bearing component (10) has an outerdiameter of an outer surface (10 a) with a first diameter (d10 a), andsaid second bearing component has an inner diameter of an inner bearingsurface (11 i) with an inner diameter (d11 i), said inner diameter beingsmaller than said outer diameter. for an axial supporting surface (10 c)between said bearing bodies (10,11) in a difference portion; for anaxial bearing surface (b,10 b) within said inner diameter; and whereinsaid radial offset (dr), said inner diameter, and said outer diameter ofa respective sleeve are coordinated such that a circumferentiallyextending face end or strip portion (10 c,10 b,b) is provided, as one ofan axial support when permanently fixing said second bearing body and anoperational bearing (b) of at least one rotatable part of saidmicrosystem (M), particularly of one of said outer rotor and said innerrotor.
 18. The method of claim 17, wherein said strip portion as a faceend surface (10 b) does not have a constant width (b) along itscircumferential extension.
 19. The method of claim 1, wherein thebearing portion is constructed of one of hardened steel, ceramic, andhard metal.
 20. Microsystem with a fluidal flow, said microsystemcomprising a first portion for one of an inlet and an outlet of a fluid(F) and a second portion having at least one bearing portion (10,11),wherein (a) a rotor (40,2) is rotatably supported relative to a stator(30) by at least one bearing body (10,11), said bearing body beingprefabricated of a hard material; (b) said stator (30) comprises aninner surface portion (30 i,30 i′) receiving said bearing body (10,11),said inner surface portion being made of a softer material than saidbearing body.
 21. The microsystem of claim 20, wherein two bearingbodies (10,11) are made of said hard material and positioned in saidstator.
 22. The microsystem of claim 21, wherein two bearing bodies areradially offset relative to each other and are arranged in said statorsuch that a respective center axis (100,101) of a respective bearingbody (10,11) has a radial distance from the other (dr) axis.
 23. Themicrosystem of claim 20, comprising two axially offset (dL), but closelyneighboring bearing positions as separate bearing bodies (10,11) in saidstator (30).
 24. The microsystem of claim 20, wherein said stator (30)comprises as an inner portion an initially not fitting receiving portion(30 i′, 30 i) for said bearing body (10,11).
 25. The microsystem ofclaim 24, wherein, when inserting said bearing body into said notfitting portion, said initially not fitting portion and said at leastone bearing body (10,11) form a gap, said gap having a width of largerthan zero, and a hardening filling material is introduced into said gap(13), for fixing said bearing body relative to said stator after ahardening of said filling material (12).
 26. The microsystem of claim20, wherein said initially not fitting portion is an undersize of saidreceiving portion (30 i′,30 i) of said stator, into which a bearing body(10,11) is mechanically pressed by friction setting, said bearing bodybeing radially larger than said receiving portion and made of a hardermaterial, thus displacing part of said receiving portion of said stator(30), but at least modifying said receiving portion with respect to itssurface structure.
 27. Method for at least one of manufacturing,adapting and adjusting at least one bearing portion in a fluidal mini tomicro system (M), said system comprising a stator (30) and at least onerotor (40,2), said rotor being rotatably supported at said at least onebearing portion (L10,L11) to be rotatable relative to said stator,characterized in that (a) said stator, prior to inserting at least oneseparate bearing body, comprises a portion (30 i,30 i′) not suitable fora bearing support, said portion being made of a softer material thansaid bearing body (10,11) (as a non-fitting portion or misfit); (b) saidnon-fitting portion, by inserting, particularly by pressing in or gluingin, said bearing body made of a harder material with respect to thematerial of said stator, is provided as a mechanical assembly andadjusting portion, for spatially-geometrically, high-preciselydetermining an inner surface (11 i,10 i) defined by said bearing body asa bearing surface for rotatably supporting said rotor (40,2).
 28. Themethod of claim 27, wherein said pressing in is effected by displacing,but at least by modifying an inner surface (30 i) of said bearing body.29. The method of claim 28, wherein a hardening material (12) isintroduced into one of a gap and, subsequently to said mechanicaldisplacement, the remaining interspaces, for obtaining a mechanicalfixing and a spatial/geometrical positioning of said bearing body as abearing portion after hardening of said filling material (12).
 30. Themethod of claim 1, wherein said bearing component (10,11) has at leastone of an outer diameter of less than 15 mm, particularly less than 10mm, and an inner diameter of less than 5 mm, particularly less than 2mm, for supporting an outer rotor (2), particularly a shaft (40). 31.The method of claim 27, wherein two bearing portions (L10,L11) aredetermined successively, one by friction setting (10 a,10 i) and afurther one by soldering, gluing in (11 a,11 i) or friction setting. 32.The method of claim 31, wherein initially friction setting andthereafter gluing in takes place.
 33. The method of claim 27; whereintwo bearing portions (L10,L11) are determined successively, one byfriction setting (10 a,10 i) and a further one by soldering, gluing in(11 a,11 i) or friction setting; and wherein initially friction settingand thereafter gluing in takes place; and wherein said first bearingportion inserted by friction setting is used as an auxiliary bearingportion determined relatively to said stator (30), forspatially/geometrically positioning said second bearing portion (L11)prior to fixing/locating it by said hardening material (12).
 34. Themethod of claim 27, wherein two bearing portions (L10,L11) aredetermined successively, one by friction setting (10 a,10 i) and afurther one by soldering, gluing in (11 a,11 i) or friction setting; andwherein said first bearing portion inserted by friction setting is usedas an auxiliary bearing portion determined relatively to said stator(30), for spatially/geometrically positioning said second bearingportion (L11) prior to fixing/locating it by said hardening material(12); and wherein said second bearing portion (11;11 a,11 i) ispositioned in at least one of an axial (10 b) and a radial (10 i,11 i)direction, supported by said first bearing portion (10).
 35. Method formanufacturing a first and a second bearing portion for two rotatingbodies (2,40) and forming a joint system of a stator and rotors,rotatable relative to said stator, wherein said mechanically precisejoint system is obtained from two bearing portions (L10,L11) andcorresponding two rotors (2,40) by simple, butmechanically/geometrically precise bodies (10,11) and a stator (30) notprecise enough for a bearing support, and by a permanent connectingtechnology, permanently fixing said precise bodies with respect to eachother and with respect to said stator; by subsequently inserting andbearingly supporting said two rotors (2,40) in said stator (30;10,11)adapted for a bearing support by said connecting technology and saidprecise bodies (10,11).